1. Field of the Invention
The present invention relates to a digital communication system, and more particularly to an apparatus and a method for generating decoding clock signals in response to a period of write and read clock signals for decoding transmission data, which is suppressed in a form of punctured code at a code rate.
2. Description of the Related Art
In a digital communication network, a transmission part transmits to a receiving part a data suppressed in a form of punctured code and the receiving part decodes the suppressed data according to a code rate. At the receiving part, the type of data suppression depends upon the code rate.
FIG. 1 is a schematic diagram illustrating an output format of data suppressed at a code rate. In FIG. 1, I and Q denote suppressed output data and X and Y denote original data. As shown in FIG. 1, in case of the code rate of 2/3, the transmission part transmits to the receiving part the data which is suppressed by using six data out of eight data. That is, the transmission part transmits the suppressed data I and Q consisting of six data out of eight data of X1, X2, X3, X4, Y1, Y2, Y3 and Y4, exclusive of data of X2 and X4, according to the code rate.
On the other hand, in case of the code rate of 3/4, the transmission part transmits to the receiving part the suppressed data I and Q consisting of four data out of six data of X1 , X2, X3, Y1, Y2 and Y3, exclusive of data of X2 and Y3, according to the code rate. Also, in case of the code rate of 5/6, the transmission part transmits to the receiving part the suppressed data I and Q consisting of six data out of ten data of X1, X2, X3, X4, X5, Y1, Y2, Y3, Y4 and Y5, exclusive of data of X2, X4, Y3 and Y5, according to the code rate. Further, in case of the code rate of 7/8, the transmission part transmits to the receiving part the suppressed data I and Q consisting of eight data out of fourteen data of X1, X2, X3, X4, X5 , X6, X7, Y1, Y2, Y3, Y4, Y5, Y6 and Y7, exclusive of data of X2, X3, X4, X5 , Y6 and Y7, according to the code rate.
The punctured code is decoded into the originally non-punctured code at the receiving part. In other words, the receiving part obtains the original data (X and Y) from the suppressed data (I and Q) and the code rate, by decoding the data deleted at the transmission part.
The conventional decoding clock generator has used system clock signals which are different in phase by using a PLL. However, the conventional decoding clock generator has a problem in that the PLL makes it complicated.